Non-lithographic hole pattern formation

ABSTRACT

A metal layer is deposited over a material layer. The metal layer includes an elemental metal that can be converted into a dielectric metal-containing compound by plasma oxidation or nitridation. A hard mask portion is formed over the metal layer. A plasma impermeable spacer is formed on at least one first sidewall of the hard mask portion, while at least one second sidewall of the hard mask portion is physically exposed. Plasma oxidation or nitridation is performed to convert physically exposed surfaces of the metal layer into the dielectric metal-containing compound. A sequence of a surface pull back of the hard mask portion, cavity etching, another surface pull back, and conversion of top surfaces into the dielectric metal-containing compound are repeated to form a hole pattern having a spacing that is not limited by lithographic minimum dimensions.

BACKGROUND

The present disclosure relates to a method of patterning a structure, and more particularly to a non-lithographic method of patterning a structure employing successive mask erosion, and structures formed by the same.

Semiconductor device scaling has been limited by the limitations of lithographic tools. For example, dimensions of minimum printable features have been limited by the capabilities of available lithographic tools to print such features. The slow progress in the capabilities of lithographic tools in recent years has made it difficult to aggressively scale the pitch of line level patterns near critical dimensions.

SUMMARY

A metal layer is deposited over a material layer. The metal layer includes an elemental metal that can be converted into a dielectric metal-containing compound by plasma oxidation or nitridation. A hard mask portion is formed over the metal layer. A plasma impermeable spacer is formed on at least one first sidewall of the hard mask portion, while at least one second sidewall of the hard mask portion is physically exposed. Plasma oxidation or nitridation is performed to convert physically exposed surfaces of the metal layer into the dielectric metal-containing compound. Surface portions of the hard mask portion are pulled back to physically expose surfaces of the metal layer, and cavities are formed through the metal layer in the newly exposed area. Additional surface portions of the hard mask portion are pulled back, and physically exposed top surfaces of the metal layer are converted into the dielectric metal-containing compound. The sequence of a surface pull back of the hard mask portion, cavity etching, another surface pull back, and conversion of top surfaces into the dielectric metal-containing compound are repeated to form a hole pattern having a spacing that is not limited by lithographic minimum dimensions.

According to an aspect of the present disclosure, a method of forming a patterned structure is provided. A metal layer is formed on a material layer. A hard mask portion is formed on the metal layer. A plasma-resistant spacer is formed on sidewalls of the hard mask portion. At least one sidewall of the hard mask portion is physically exposed by removing a portion of the plasma-resistant spacer. A first surface portion of the metal layer is converted into a dielectric metal-containing compound portion employing the hard mask portion and a remaining portion of the plasma-resistant spacer as masking structures.

According to another aspect of the present disclosure, a patterned structure is provided, which includes a patterned layer located on a material layer. The patterned layer includes a metal layer and a dielectric metal-containing compound portion embedded in an upper portion of the metal layer. The patterned structure further includes a hard mask portion contacting a top surface of the metal layer. In addition, the patterned structure includes a plasma-resistant spacer contacting a first sidewall of the hard mask portion. A second sidewall of the hard mask portion is physically exposed.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a top-down view of an exemplary structure after formation of a metal layer and patterned hard mask portions according to an embodiment of the present disclosure.

FIG. 1B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 1A.

FIG. 2A is a top-down view of the exemplary structure after formation of plasma-resistant spacers according to an embodiment of the present disclosure.

FIG. 2B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 2A.

FIG. 3A is a top-down view of the exemplary structure after application and patterning of a photoresist layer according to an embodiment of the present disclosure.

FIG. 3B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 3A.

FIG. 4A is a top-down view of the exemplary structure after patterning of the hard mask portions and plasma-resistant spacers according to an embodiment of the present disclosure.

FIG. 4B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 4A.

FIG. 5A is a top-down view of the exemplary structure after formation of a dielectric metal-containing compound portions according to an embodiment of the present disclosure.

FIG. 5B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 5A.

FIG. 6A is a top-down view of the exemplary structure after a pull back of the hard mask portions according to an embodiment of the present disclosure.

FIG. 6B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 6A.

FIG. 7A is a top-down view of the exemplary structure after formation of cavities through the metal layer according to an embodiment of the present disclosure.

FIG. 7B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 7A.

FIG. 7C is a vertical cross-sectional view of the exemplary structure along the vertical plane C-C′ of FIG. 7A.

FIG. 8A is a top-down view of the exemplary structure after a pull back of the hard mask portions according to an embodiment of the present disclosure.

FIG. 8B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 8A.

FIG. 9A is a top-down view of the exemplary structure after formation of additional dielectric metal-containing compound portions according to an embodiment of the present disclosure.

FIG. 9B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 9A.

FIG. 10A is a top-down view of the exemplary structure after a pull back of the hard mask portions according to an embodiment of the present disclosure.

FIG. 10B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 10A.

FIG. 11A is a top-down view of the exemplary structure after formation of additional cavities through the metal layer according to an embodiment of the present disclosure.

FIG. 11B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 11A.

FIG. 12A is a top-down view of the exemplary structure after repeatedly performing the sequence of a pull back of the hard mask portions, formation of additional dielectric metal-containing compound portions, another pull back of the hard mask portions, and formation of additional cavities according to an embodiment of the present disclosure.

FIG. 12B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 12A.

FIG. 13A is a top-down view of the exemplary structure after transfer of the pattern in the metal layer into a material layer by an anisotropic etch according to an embodiment of the present disclosure.

FIG. 13B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 13A.

FIG. 14A is a top-down view of the exemplary structure after removal of the dielectric metal-containing compound layer and the metal layer according to an embodiment of the present disclosure.

FIG. 14B is a vertical cross-sectional view of the exemplary structure along the vertical plane B-B′ of FIG. 14A.

FIG. 15 is a vertical cross-sectional view of a variation of the exemplary structure according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

As stated above, the present disclosure relates to a non-lithographic method of patterning a structure employing successive mask erosion, and structures formed by the same. Aspects of the present disclosure are now described in detail with accompanying figures. It is noted that like reference numerals refer to like elements across different embodiments. The drawings are not necessarily drawn to scale.

Referring to FIGS. 1A and 1B, an exemplary structure according to an embodiment of the present disclosure comprises an optional handle substrate 10 and a material layer 20 located on the optional handle substrate 10. The optional handle substrate 10, if present, can include a dielectric material, a conductive material, a semiconductor material, or a combination thereof. When present, the optional handle substrate 10 can provide mechanical support to the material layer 20.

The material layer 20 can include a semiconductor material, a dielectric material, a conductive material, or a combination thereof. The material layer 20 may include a material different from, or the same as, the material of the optional handle substrate 10. For example, the material layer 20 can include a single crystalline semiconductor material or a polycrystalline semiconductor material, and the optional handle substrate 10 can include a dielectric material or a semiconductor material different from the semiconductor material of the material layer 20.

A metal layer 30 can be formed on the top surface of the material layer 20. The metal layer 30 includes a metal that can be converted into a metal-containing compound. In one embodiment, the metal containing compound can be a dielectric metal containing oxide, a dielectric metal-containing nitride, or a dielectric metal-containing oxynitride. In one embodiment, the metal layer 30 can include an elemental metal. Non-limiting examples of the elemental metal include aluminum, tantalum, titanium, tungsten, hafnium, zirconium, chromium, copper, zinc, iron, cobalt, and nickel.

In one embodiment, the metal layer includes at least one elemental metal that can be converted into a dielectric metal-containing oxide. Elemental metals that can be converted into a dielectric metal-containing oxide include, but are not limited to, aluminum, tantalum, titanium, tungsten, hafnium, zirconium, chromium, copper, zinc, iron, cobalt, and nickel.

In another embodiment, the metal layer includes at least one elemental metal that can be converted into a dielectric metal-containing nitride. Elemental metals that can be converted into a dielectric metal-containing nitride include, but are not limited to, aluminum, tantalum, titanium, tungsten, hafnium, zirconium, chromium, copper, zinc, iron, cobalt, and nickel.

The metal layer 30 can be deposited by physical vapor deposition (PVD), chemical vapor deposition (CVD), electroplating, electroless plating, or combinations thereof. The thickness of the metal layer 30 can be, for example, from 10 nm to 300 nm, although lesser and greater thicknesses can also be employed. The metal layer 30 can be deposited as a blanket layer having a same thickness throughout.

A hard mask layer is deposited over the metal layer 30. The hard mask layer may include a dielectric material such as silicon oxide, silicon nitride, silicon oxynitride, or combinations thereof. The hard mask layer can be deposited as a blanket having a same thickness throughout. The thickness of the hard mask layer can be from 30 nm to 1,000 nm, although lesser and greater thicknesses can also be employed.

The hard mask layer is lithographically patterned to form hard mask portions 40. Specifically, a photoresist layer (not shown) is applied over the top surface of the hard mask layer, and is subsequently lithographically patterned to form photoresist portions that cover discrete areas over the hard mask layer. The pattern in the photoresist portions can be transferred into the hard mask layer by an anisotropic etch. The remaining portions of the hard mask layer constitute the hard mask portions 40. The photoresist portions can be subsequently removed selective to the hard mask portions 40 and the metal layer 30, for example, by ashing.

Referring to FIGS. 2A and 2B, a conformal dielectric material layer can be deposited on surfaces of the hard mask portions 40 and physically exposed surface of the metal layer 30. The conformal dielectric material layer includes a plasma-resistant material. As used herein, a material is “plasma-resistant” if the material is not consumed by a plasma of oxygen, nitrogen, or a combination thereof that has an energy that is sufficient to convert a surface of a metal into a metal oxide, a metal nitride, or a metal oxynitride.

In one embodiment, the conformal dielectric material layer includes a dielectric metal oxide, a dielectric metal nitride, or a dielectric metal oxynitride. Examples of the dielectric metal oxide that can be employed for the conformal dielectric material layer include, but are not limited to, hafnium oxide, zirconium oxide, tantalum oxide, and titanium oxide. Examples of the dielectric metal nitride that can be employed for the conformal dielectric material layer include, but are not limited to, hafnium nitride, zirconium nitride, tantalum nitride, and titanium nitride. Examples of the dielectric metal oxynitride that can be employed for the conformal dielectric material layer include, but are not limited to, hafnium oxynitride, zirconium oxynitride, tantalum oxynitride, and titanium oxynitride. The conformal dielectric material layer can be deposited, for example, by chemical vapor deposition (CVD) or atomic layer deposition (ALD). The thickness of the conformal dielectric material layer can be from 1 nm to 60 nm, although lesser and greater thicknesses can also be employed.

Horizontal portions of the conformal dielectric material layer are removed by an anisotropic etch, which can be a reactive ion etch. The reactive ion etch can employ, for example, a chlorine plasma. Each remaining vertical portions of the conformal dielectric material layer constitute a plasma-resistant spacer 42, which is present on sidewalls of a hard mask portion 40.

Referring to FIGS. 3A and 3B, a photoresist layer 47 is applied over the metal layer 30, the hard mask portions 40, and the etch-resistant spacers 42, for example, by spin coating. The photoresist layer 47 is subsequently patterned by lithographic exposure and development.

In one embodiment, the photoresist layer 47 is patterned such that at least one edge of the patterned photoresist overlies each hard mask portion 42. In one embodiment, for each hard mask portion 40 and an etch-resistant spacer 42 laterally contacting sidewalls of the hard mask portion 40, there exists an edge of the patterned photoresist layer 47 that straddles over the hard mask portion 40 and the etch-resistant spacer 42.

An edge of the patterned photoresist layer 47 can overlie a hard mask portion 40 and an etch-resistant spacer 42 contacting the hard mask portion 42 in any orientation relative to the orientation of the hard mask portion 40. In one embodiment, a hard mask portion 40 can have a rectangular horizontal cross-sectional area, and an edge of the patterned photoresist layer 47 can overlie the hard mask portion 40 along a direction that is perpendicular to the lengthwise direction of the hard mask portion 40. In another embodiment, a hard mask portion 40 can have a rectangular horizontal cross-sectional area, and an edge of the patterned photoresist layer 47 can overlie the hard mask portion 40 along the lengthwise direction of the hard mask portion 40.

Referring to FIGS. 4A and 4B, sub-portions of the hard mask portions 40 that are not covered by the patterned photoresist layer 47 and portions of the plasma-resistant spacers 42 that are not covered by the patterned photoresist layer 47 are removed by at least one etch that employs the patterned photoresist layer as an etch mask. The etch chemistry of the at least one etch can be selected to etch the materials of the hard mask portions 40 and the plasma-resistant spacers 42. The at least one etch can include an etch that removes the material of the hard mask portions 40 and another etch that removes the material of the plasma-resistant spacers 42. In one embodiment, a combination of an anisotropic etch that removes the material of the hard mask portions 40 and a wet etch that removes the material of the plasma-resistant spacers 42 can be employed. Etch chemistries known in the art can be employed for the at least one etch. The patterned photoresist layer 47 is subsequently removed, for example, by ashing. At least a portion of each plasma-resistant spacer 42 is removed by the at least one etch, and at least one sidewall of each hard mask portion 40 is physically exposed.

A surface portion of the metal layer 30 is physically exposed within an area in which the hard mask portions 40 or the plasma-resistant spacers 42 are not present. As used herein, a “surface portion” refers to a portion of a structure that is located directly beneath a physically exposed surface of a structure and not extending to surface of the structure that is located on an opposite side of the physically exposed surface. The surface portion of the metal layer 30 that is physically exposed at this step is herein referred to as a first surface portion.

Referring to FIGS. 5A and 5B, the first surface portion of the metal layer 30 is converted into a dielectric metal-containing compound portion, which is herein referred to as a first dielectric metal-containing compound portion 32A. The conversion of the first surface portion of the metal layer 30 into the first dielectric metal-containing compound portion 32A can be performed employing a plasma conversion process. The hard mask portions 40 and the plasma-resistant spacers 42 can be employed as masking structures that mask the portions of the metal layer 30 underneath the hard mask portions 40 and the plasma-resistant spacers 42 from conversion into a dielectric metal-containing compound material.

In one embodiment, the conversion of the first surface portion of the metal layer 30 into the first dielectric metal-containing compound portion 32A can be performed by plasma oxidation, in which an oxygen-containing plasma oxidizes the first surface portion of the metal layer 30 into a metal oxide material. The plasma oxidation can employ a plasma of oxygen or ozone within a pressure range from 0.1 mTorr to 10 mTorr, although lesser and greater pressures can also be employed. The first dielectric metal-containing compound portion 32A includes an oxide of the metal of the metal layer 30. The thickness of the first dielectric metal-containing compound portion 32A is determined by the energy of the oxygen-containing plasma and duration of the plasma oxidation process, and can be from 0.6 nm to 10 nm, although lesser and greater thicknesses can also be employed. For example, if the metal of the metal layer 30 is aluminum, the dielectric metal-containing compound can be aluminum oxide. If the metal of the metal layer 30 is a transition metal, the dielectric metal-containing compound can be a transition metal oxide.

In another embodiment, the conversion of the first surface portion of the metal layer 30 into the first dielectric metal-containing compound portion 32A can be performed by plasma nitridation, in which a nitrogen-containing plasma nitridates the first surface portion of the metal layer 30 into a metal nitride material. The plasma nitridation can employ a plasma of nitrogen or ammonia within a pressure range from 0.1 mTorr to 10 mTorr, although lesser and greater pressures can also be employed. The first dielectric metal-containing compound portion 32A includes a nitride of the metal of the metal layer 30. The thickness of the first dielectric metal-containing compound portion 32A is determined by the energy of the nitrogen-containing plasma and duration of the plasma nitridation process, and can be from 0.6 nm to 10 nm, although lesser and greater thicknesses can also be employed. For example, if the metal of the metal layer 30 is aluminum, the dielectric metal-containing compound can be aluminum nitride. If the metal of the metal layer 30 is a transition metal, the dielectric metal-containing compound can be a transition metal nitride.

In yet another embodiment, the conversion of the first surface portion of the metal layer 30 into the first dielectric metal-containing compound portion 32A can be performed by plasma oxynitridation, in which a plasma containing oxygen and nitrogen converts the first surface portion of the metal layer 30 into a metal oxynitride material. The plasma oxynitridation can employ a plasma of an oxidizing species and a nitridating species within a pressure range from 0.1 mTorr to 10 mTorr, although lesser and greater pressures can also be employed. The oxidizing species can be at least one of oxygen and ozone, and the nitridating species can be at least one of nitrogen and ammonia. The first dielectric metal-containing compound portion 32A includes an oxynitride of the metal of the metal layer 30. The thickness of the first dielectric metal-containing compound portion 32A is determined by the energy of the plasma and duration of the plasma oxynitridation process, and can be from 0.6 nm to 10 nm, although lesser and greater thicknesses can also be employed.

The exemplary structure includes a patterned layer (30, 32A) located on the material layer 20. The patterned layer (30, 32A) includes the metal layer 30 and the first dielectric metal-containing compound portion 32A embedded in an upper portion of the metal layer 30. The hard mask portions 40 contact top surfaces of the metal layer 30. Each plasma-resistant spacers 42 contact a first sidewall of a hard mask portion 40, and a second sidewall of the hard mask portion 40 is physically exposed.

Referring to FIGS. 6A and 6B, the hard mask portions 40 are isotropically etched, for example, by a wet etch or a vapor phase etch. The etch-resistant spacers 42 protect portions of the hard mask portions 40 by blocking access of a wet chemical or an etchant vapor to the protected portions of the hard mask portions 40. The physically exposed surfaces of the hard mask portions 40 are pulled back isotropically, i.e., move away from the position prior to the etch toward a center sub-portion of each hard mask portion 40 by the etch. The chemistry of the isotropic etch can be selected such that the material of the hard mask portions 40 is removed without substantially removing the metal in the metal layer 30 or the dielectric metal-containing compound in the first dielectric metal-containing compound portion 32A.

In one embodiment, the hard mask portions 40 can include silicon oxide, and the isotropic etch can employ hydrofluoric acid-based etch chemistry. In another embodiment, the hard mask portions 40 can include silicon nitride, and the isotropic etch can employ an etch chemistry based on hot phosphoric acid. Physically exposed lateral surfaces and top surfaces of the hard mask portions 40 are recessed during the isotropic etch.

Top surfaces the metal layer 30 are physically exposed after the physically exposed surfaces of the hard mask portions 40 are isotropically recessed by the isotropic etch. Each surface portion of the metal layer 30 located directly beneath the physically exposed top surfaces of the metal layer 30 is herein referred to as a second surface portion of the metal layer 30. In one embodiment, an outer edge of each second surface portion coincides with an inner edge of the first dielectric metal-containing compound portion 32A.

The distance of lateral recess of the hard mask portions 40 is the same irrespective of location of the physically exposed surfaces of the hard mask portions 40. Thus, each second surface portion of the metal layer 30 has a same width throughout. In one embodiment, the width of each second surface portion of the metal layer 30 can be from 1 nm to 100 nm, although lesser and greater widths can also be employed. The width of the second surfaces portions of the metal layer 30 is not limited by any lithographic capabilities of available lithography tools because the width is determined by the etch rate and the duration of the etch process employed to recess the physically exposed surfaces of the hard mask portions 40.

Referring to FIGS. 7A, 7B, and 7C, first cavities 33 are formed through the metal layer 30 by anisotropically etching the second surface portions and the portions of the metal layer 30 that underlie the second surface portions employing the first dielectric metal-containing compound portion 32A, the hard mask portions 40, and the plasma-resistant spacers 42 as etch masks. The first cavities 33 are formed through the metal layer 30 within the area of the second surface portions of the metal layer 30, which is the area in which top surfaces of the metal layer 30 are physically exposed. The first cavities 33 are formed by an anisotropic etch that removes the metal in the metal layer 30 selective to the dielectric metal-containing compound in the first dielectric metal-containing compound portion 32A and selective to the materials of the hard mask portions 40 and the plasma-resistant spacers 42. For example, chlorine-based etch chemistry can be employed to remove the metal in the metal layer 30 selective to the dielectric metal-containing compound of the first dielectric metal-containing compound portion 32A, and selective to the dielectric materials of the hard mask portions 40 and the plasma-resistant spacers 42. Etch gases that can be employed for the chlorine-based etch chemistry include, but are not limited to, Cl₂, CCl₄, CHCl₃, CH₂Cl₂, and combinations thereof.

In one embodiment, the material layer 20 can be selected to be a material that is resistant to the etch chemistry of the anisotropic etch that forms the first cavities 33. For example, the material at the top surface of the material layer 20 can be a dielectric material such as silicon oxide, silicon nitride, silicon oxynitride, a dielectric metal oxide, a semiconductor material, or a combination thereof.

Each first cavity 33 extends from a top surface of the first dielectric metal-containing compound portion 32A to a bottom surface of the metal layer 30. A sidewall of each first cavity 33 can be vertically coincident with a sidewall of the first dielectric metal-containing compound portion 32A. As used herein, a first surface of a first element is “vertically coincident” with a second surface of a second element if the first surface and the second surface are within a same vertical plane. Another sidewall of each first cavity 33 can be vertically coincident with a sidewall of a plasma-resistant spacer 42.

Further, a sidewall of each hard mask portion 40 can be vertically coincident with a sidewall of a first cavity 33. A sidewall of a portion of the metal layer 33 can be vertically coincident with a sidewall of a first cavity 33.

Referring to FIGS. 8A and 8B, the hard mask portions 40 are isotropically etched, for example, by a wet etch or a vapor phase etch. The etch-resistant spacers 42 protect portions of the hard mask portions 40 by blocking access of a wet chemical or an etchant vapor to the protected portions of the hard mask portions 40. The physically exposed surfaces of the hard mask portions 40 are pulled back isotropically by the isotropic etch. The chemistry of the isotropic etch can be selected such that the material of the hard mask portions 40 is removed without substantially removing the metal in the metal layer 30 or the dielectric metal-containing compound in the first dielectric metal-containing compound portion 32A. In one embodiment, the same etch chemistry can be employed as in the isotropic etch performed in the processing steps of FIGS. 6A and 6B.

Top surfaces the metal layer 30 are physically exposed after the physically exposed surfaces of the hard mask portions 40 are isotropically recessed by the isotropic etch. Each surface portion of the metal layer 30 located directly beneath the physically exposed top surfaces of the metal layer 30 is herein referred to as a third surface portion of the metal layer 30. In one embodiment, an outer edge of each third surface portion coincides with an inner edge of the first cavities 33.

The distance of lateral recess of the hard mask portions 40 is the same irrespective of location of the physically exposed surfaces of the hard mask portions 40. Thus, each third surface portion of the metal layer 30 has a same width throughout. In one embodiment, the width of each third surface portion of the metal layer 30 can be from 1 nm to 100 nm, although lesser and greater widths can also be employed. The width of the third surfaces portions of the metal layer 30 is not limited by any lithographic capabilities of available lithography tools because the width is determined by the etch rate and the duration of the etch process employed to recess the physically exposed surfaces of the hard mask portions 40.

Referring to FIGS. 9A and 9B, the third surface portions of the metal layer 30 are converted into dielectric metal-containing compound portions, which are herein referred to as second dielectric metal-containing compound portions 32B. The conversion of the third surface portions of the metal layer 30 into the second dielectric metal-containing compound portions 32B can be performed employing a plasma conversion process. The hard mask portions 40 and the plasma-resistant spacers 42 can be employed as masking structures that mask the portions of the metal layer 30 underneath the hard mask portions 40 and the plasma resistant spacers 42 from conversion into a dielectric metal-containing compound material.

In one embodiment, the conversion of the third surface portions of the metal layer 30 into the second dielectric metal-containing compound portions 32B can be performed by plasma oxidation, in which an oxygen-containing plasma oxidizes the third surface portions of the metal layer 30 into a metal oxide material. The processing parameters of the plasma oxidation process can be the same as the plasma oxidation process that can be employed at the processing steps of FIGS. 5A and 5B.

In another embodiment, the conversion of the third surface portions of the metal layer 30 into the second dielectric metal-containing compound portions 32B can be performed by plasma nitridation, in which a nitrogen-containing plasma nitridates the third surface portions of the metal layer 30 into a metal nitride material. The processing parameters of the plasma nitridation process can be the same as the plasma nitridation process that can be employed at the processing steps of FIGS. 5A and 5B.

In yet another embodiment, the conversion of the third surface portions of the metal layer 30 into the second dielectric metal-containing compound portions 32B can be performed by plasma oxynitridation, in which a plasma containing oxygen and nitrogen converts the third surface portions of the metal layer 30 into a metal oxynitride material. The processing parameters of the plasma oxynitridation process can be the same as the plasma oxynitridation process that can be employed at the processing steps of FIGS. 5A and 5B.

In one embodiment, the processing parameters of the plasma oxidation, plasma nitridation, or plasma oxynitridation can be selected so that ions of the plasma impinge substantially vertically on the surfaces of the metal layer 30. In this case, the second dielectric metal-containing compound portions 32B can be formed only beneath horizontal surfaces of the metal layer 30.

The exemplary structure illustrated in FIGS. 9A and 9B is a patterned structure including a patterned layer (30, 32A, 32B) located on the material layer 20. The patterned layer (30, 32A, 32B) includes the first dielectric metal-containing compound portion 32A, second dielectric metal-containing compound portions 32B, and the metal layer 30 that embeds the first and second dielectric metal-containing compound portions (32A, 32B). The entirety of the metal layer 30 is contiguous, i.e., constitutes a single undivided physical structure.

In one embodiment, a portion of the metal layer 30 that contacts a hard mask portion 40 can have the same thickness as a stack of a dielectric metal-containing compound portion, such as the first dielectric metal-containing compound portion 32A or the second dielectric metal-containing compound portions 32B, and an underlying portion of the metal layer 30. In one embodiment, a sidewall of each hard mask portion 40 can vertically coincide with a substantially vertical interface between the metal layer 30 and a second dielectric metal-containing compound portion 32B.

Referring to FIGS. 10A and 10B, the hard mask portions 40 are isotropically etched, for example, by a wet etch or a vapor phase etch. The etch-resistant spacers 42 protect portions of the hard mask portions 40 by blocking access of a wet chemical or an etchant vapor to the protected portions of the hard mask portions 40. The physically exposed surfaces of the hard mask portions 40 are pulled back isotropically by the isotropic etch. The chemistry of the isotropic etch can be selected such that the material of the hard mask portions 40 is removed without substantially removing the metal in the metal layer 30 or the dielectric metal-containing compound in the first and second dielectric metal-containing compound portions (32A, 32B). In one embodiment, the same etch chemistry can be employed as in the isotropic etch performed in the processing steps of FIGS. 6A and 6B.

Top surfaces the metal layer 30 are physically exposed after the physically exposed surfaces of the hard mask portions 40 are isotropically recessed by the isotropic etch. Each surface portion of the metal layer 30 located directly beneath the physically exposed top surfaces of the metal layer 30 is herein referred to as a fourth surface portion of the metal layer 30. In one embodiment, an outer edge of each fourth surface portion coincides with an inner edge of a second dielectric metal-containing compound portion 32B.

The distance of lateral recess of the hard mask portions 40 is the same irrespective of location of the physically exposed surfaces of the hard mask portions 40. Thus, each fourth surface portion of the metal layer 30 can have a same width throughout. In one embodiment, the width of each fourth surface portion of the metal layer 30 can be from 1 nm to 100 nm, although lesser and greater widths can also be employed. The width of the fourth surfaces portions of the metal layer 30 is not limited by any lithographic capabilities of available lithography tools because the width is determined by the etch rate and the duration of the etch process employed to recess the physically exposed surfaces of the hard mask portions 40.

Referring to FIGS. 11A and 11B, second cavities 33′ are formed through the metal layer 30 by anisotropically etching the fourth surface portions and the portions of the metal layer 30 that underlie the fourth surface portions employing the first and second dielectric metal-containing compound portions (32A, 32B) and the hard mask portions 40 as etch masks. The second cavities 33′ are formed through the metal layer 30 within the area of the fourth surface portions of the metal layer 30, which is the area in which top surfaces of the metal layer 30 are physically exposed. The second cavities 33 are formed by an anisotropic etch that removes the metal in the metal layer 30 selective to the dielectric metal-containing compound in the first and second dielectric metal-containing compound portions (32A, 32B) and selective to the material of the hard mask portions 40. For example, chlorine-based etch chemistry can be employed to remove the metal in the metal layer 30 selective to the dielectric metal-containing compound of the first dielectric metal-containing compound portions (32A, 32B), and selective to the dielectric material of the hard mask portions 40.

Referring to FIGS. 12A and 12B, a sequence of a pull back of the hard mask portions 40, formation of additional dielectric metal-containing compound portions, another pull back of the hard mask portions 40, and formation of additional cavities can be optionally repeated. Specifically, the step of physically exposing a top surface of additional surface portions of the metal layer 30 by isotropically recessing physically exposed surfaces of the hard mask portions 40 can be performed employing the same processing steps as the processing steps of FIGS. 8A and 8B. The step of converting the additional surface portions of the metal layer 30 into additional dielectric metal-containing compound portions (such as a third dielectric metal-containing compound portion 32C) employing the hard mask portions 40 and the plasma-resistant spacers 42 as masking structures can be performed employing the same processing steps as the processing steps of FIGS. 9A and 9B. The step of physically exposing a top surface of yet additional surface portions of the metal layer 30 by isotropically recessing physically exposed surfaces of the hard mask portions 30 can be performed employing the same processing steps as the processing steps of FIGS. 10A and 10B. The step of forming additional cavities 33″ through the metal layer 30 by anisotropically etching the yet additional surface portions and portions of the metal layer 30 that underlies the yet additional surface portions can be performed employing the same processing steps as the processing steps of FIGS. 11A and 11B.

The sequence of a pull back of the hard mask portions 40, formation of additional dielectric metal-containing compound portions, another pull back of the hard mask portions 40, and formation of additional cavities can be optionally repeated as many times as needed or until the hard mask portions 40 are completely consumed by the repeated isotropic etching. Additional cavities 33′ can be formed through the patterned layer including the metal layer 30 and the various dielectric metal-containing compound portions (32A, 32B, 32C, 32D, 32E). The various dielectric metal-containing compound portions (32A, 32B, 32C, 32D, 32E) collectively constitute a dielectric metal-containing compound layer.

Portions of the metal layer contact the plasma-resistant spacers 42. In one embodiment, interfaces between the metal layer 30 and the plasma-resistant spacers 42 can be coplanar with the topmost surfaces of the various dielectric metal-containing compound portions (32A, 32B, 32C, 32D, 32E).

Referring to FIGS. 13A and 13B, the pattern defined by the various trenches (33, 33′, 33″, 33′″) within the patterned layer (30, 32A, 32B, 32C, 32D, 32E) is transferred into the material layer 20 by an anisotropic etch. The combination of the various dielectric metal-containing compound portions (32A, 32B, 32C, 32D, 32E) and the plasma-resistant spacers 42 can be employed as an etch mask during the anisotropic etch that transfers the pattern of the various cavities (33, 33′, 33″, 33′″) into the material layer 20. Additionally or alternately, the metal layer 30 can be employed as an etch mask layer.

The etch chemistry of the anisotropic etch can be selected so that the material of the material layer 20 can be etched selective to at least one of the dielectric metal-containing compound of the various dielectric metal-containing compound portions (32A, 32B, 32C, 32D, 32E) and the metal of the metal of the metal layer 30. In one embodiment, the anisotropic etch can have an etch chemistry that removes the material of the material layer 20 selective to the dielectric metal-containing compound of the various dielectric metal-containing compound portions (32A, 32B, 32C, 32D, 32E) and selective to the dielectric material of the plasma-resistant spacers 42. In another embodiment, the anisotropic etch can have an etch chemistry that removes the material of the material layer 20 selective to the metal of the metal layer 30.

Referring to FIGS. 14A and 14B, the plasma-resistant spacers 42, the dielectric metal-containing compound portions (32A, 32B, 32C, 32D, 32E), and the metal layer 30 can be removed selective to the material layer 20 by at least one etch, which can include at least one wet etch and/or at least one dry etch. The removal of the etch-resistant spacers 42 can be performed, for example, by a wet etch that removes a dielectric metal oxide as known in the art. The removal of the dielectric metal-containing compound portions (32A, 32B, 32C, 32D, 32E) can be removed, for example, by an etch that employs a fluorine-based etch chemistry. For example, a dry etch employing CF₄, CHF₃, and/or CH₂F₂ can be employed. Any other etch chemistry that removes the dielectric metal-containing compound portions (32A, 32B, 32C, 32D, 32E) selective to the material of the material layer 20 can also be employed. The metal layer 30 can be removed, for example, by an etch that employs a chlorine-based etch chemistry. For example, a dry etch employing CCl₄, CHCl₃, and/or CH₂Cl₂ can be employed. Any other etch chemistry that removes the metal of the metal layer 30 selective to the material of the material layer 20 can also be employed. The width of each cavity within the material layer 20 can be uniform within each cavity. Multiple cavities that replicate the pattern of cavities that are formed at the same processing step between the processing steps of FIGS. 7A and 7B and the processing steps of FIGS. 12A and 12B.

Referring to FIG. 15, a variation of the exemplary structure can be derived from the exemplary structure in FIGS. 12A and 12B by changing the processing parameters of the plasma oxidation, plasma nitridation, or plasma oxynitridation that forms the various dielectric metal-containing compound portions (32B, 32C, 32D, 32E). Specifically, the processing parameters of the plasma oxidation, plasma nitridation, or plasma oxynitridation can be selected such that a substantial fraction of the ions of the plasma impinge on the surfaces of the metal layer 30 along non-vertical directions, i.e., directions that are different from the vertical direction. In this case, the various dielectric metal-containing compound portions 32B can be formed on sidewalls of the various trenches (33, 33′, 33″, 33′″). The processing steps of FIGS. 13A and 13B and the processing steps of FIGS. 14A and 14B can be subsequently performed to provide the same structure as illustrated in FIGS. 14A and 14B.

The methods of embodiments of the present disclosure enable patterning of trenches having lateral dimensions that are not limited by lithographic capabilities. Thus, the width and/or the spacing of the trenches can be sublithographic dimensions. Further, the use of plasma-resistant spacers enables formation of a plurality of trenches having same or different sublithographic widths along a first lateral direction and having a same lateral dimension along a second lateral direction, which is perpendicular to lengthwise sidewalls of the plasma-resistant spacers. Thus, patterns including a plurality of adjacent sublithographic-width trenches can be formed.

While the disclosure has been described in terms of specific embodiments, it is evident in view of the foregoing description that numerous alternatives, modifications and variations will be apparent to those skilled in the art. Each of the embodiments described herein can be implemented individually or in combination with any other embodiment unless expressly stated otherwise or clearly incompatible. Accordingly, the disclosure is intended to encompass all such alternatives, modifications and variations which fall within the scope and spirit of the disclosure and the following claims. 

What is claimed is:
 1. A method of forming a patterned structure comprising: forming a metal layer on a material layer; forming a hard mask portion on said metal layer; forming a plasma-resistant spacer on sidewalls of said hard mask portion; physically exposing at least one sidewall of said hard mask portion by removing a portion of said plasma-resistant spacer; and converting a first surface portion of said metal layer into a dielectric metal-containing compound portion employing said hard mask portion and a remaining portion of said plasma-resistant spacer as masking structures.
 2. The method of claim 1, wherein said converting of said first surface portion comprises plasma conversion of a metal in said metal layer into a dielectric metal-containing compound.
 3. The method of claim 2, wherein said plasma conversion is plasma oxidation and said dielectric metal-containing compound is an oxide of said metal in said metal layer.
 4. The method of claim 2, wherein said plasma conversion is plasma nitridation and said dielectric metal-containing compound is a nitride of said metal in said metal layer.
 5. The method of claim 1, wherein said plasma-resistant spacer is formed by: depositing a conformal dielectric material layer; and anisotropically etching horizontal portions of said conformal dielectric material layer, where a remaining portion of said conformal dielectric material layer is said plasma-resistant spacer.
 6. The method of claim 1, further comprising physically exposing a top surface of a second surface portion of said metal layer by isotropically recessing physically exposed surfaces of said hard mask portion while said etch-resistant spacer protects a portion of said hard mask portion from removal, wherein an outer edge of said second surface portion coincides with an inner edge of said dielectric metal-containing compound portion.
 7. The method of claim 6, further comprising forming a cavity through said metal layer by anisotropically etching said second surface portion and a portion of said metal layer that underlies said second surface portion employing said dielectric metal-containing compound portion, said hard mask portion, and said plasma-resistant spacer as etch masks.
 8. The method of claim 7, further comprising physically exposing a top surface of a third surface portion of said metal layer by isotropically recessing physically exposed surfaces of said hard mask portion after said forming of said cavity, wherein an outer edge of said third surface portion coincides with an inner edge of said cavity.
 9. The method of claim 8, further comprising converting said third surface portion of said metal layer into a second dielectric metal-containing compound portion employing said hard mask portion and said plasma-resistant spacer as masking structures.
 10. The method of claim 9, further comprising: physically exposing a top surface of a fourth surface portion of said metal layer by isotropically recessing physically exposed surfaces of said hard mask portion, wherein an outer periphery of said fourth surface portion coincides with an inner periphery of said second dielectric metal-containing compound portion; and forming another cavity through said metal layer by anisotropically etching said fourth surface portion and a portion of said metal layer that underlies said fourth surface portion.
 11. The method of claim 7, further comprising performing at least once a sequence of: physically exposing a top surface of an additional surface portion of said metal layer by isotropically recessing physically exposed surfaces of said hard mask portion; converting said additional surface portion of said metal layer into an additional dielectric metal-containing compound portion employing said hard mask portion and said plasma-resistant spacer as masking structures; physically exposing a top surface of a yet additional surface portion of said metal layer by isotropically recessing physically exposed surfaces of said hard mask portion; and forming an additional cavity through said metal layer by anisotropically etching said yet additional surface portion and a portion of said metal layer that underlies said yet additional surface portion.
 12. The method of claim 7, further comprising transferring a pattern in a dielectric metal-containing compound layer including at least said dielectric metal-containing compound portion into said material layer by an anisotropic etch employing said dielectric metal-containing compound layer as an etch mask.
 13. The method of claim 11, further comprising: removing said plasma-resistant spacer; removing said dielectric metal-containing compound layer; and removing remaining portions of said metal layer from above said material layer.
 14. A patterned structure comprising: a patterned layer located on a material layer, said patterned layer comprising a metal layer and a dielectric metal-containing compound portion embedded in an upper portion of said metal layer; a hard mask portion contacting a top surface of said metal layer; and a plasma-resistant spacer contacting a first sidewall of said hard mask portion, wherein a second sidewall of said hard mask portion is physically exposed.
 15. The patterned structure of claim 14, further comprising a cavity extending from a top surface of said dielectric metal-containing compound portion to a bottom surface of said metal layer, wherein a sidewall of said cavity is vertically coincident with a sidewall of said dielectric metal-containing compound portion.
 16. The patterned structure of claim 15, wherein another sidewall of said cavity is vertically coincident with a sidewall of said plasma-resistant spacer.
 17. The patterned structure of claim 16, further comprising another dielectric metal-containing compound portion having a sidewall that is vertically coincident with yet another sidewall of said cavity.
 18. The patterned structure of claim 16, wherein a sidewall of said hard mask portion is vertically coincident with yet another sidewall of said cavity.
 19. The patterned structure of claim 16, wherein a sidewall of a portion of said metal layer is vertically coincident with yet another sidewall of said cavity.
 20. The patterned structure of claim 14, wherein said metal layer comprises an elemental metal, and said dielectric metal-containing compound portion comprises a dielectric metal-containing compound that is an oxide, a nitride, or an oxynitride of said elemental metal. 